Non-oncogenic deletion mutants of adenoviral E1A enhance paclitaxel induced apoptosis of ovarian cancer cells

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Background: The phenotypical characteristics and spread of ovarian cancer cells, suggest intraperitoneal gene therapy of this disease. Phase I trials have been conducted to investigate the potential clinical benefits of adenoviral E1A-based gene therapy. Further gene therapeutic approaches which aim to enhance the efficacy of E1A-induced apoptosis in a multimodal approach including conventional chemotherapy are planned. However, besides tumor-suppressive effects, E1A is also known to transform rodent cells in conjunction with other factors, e.g. an activated ras oncogene. In an effort to eliminate elements favouring malignant conversion, the potential therapeutic effect of the E1AdelCR2 deletion mutant on ovarian cancer cells was studied. Methods: To avoid any selection bias, a doxycyclin-regulated system was used to express E1A wildtype protein and the mutant E1AdelCR2 lacking the p105RB-binding motif. The effects of the E1A proteins on proliferation and induction of apoptosis in ovarian carcinoma cell lines was studied with a WST-1 assay and fluorcytometric analysis of FITC labelled AnnexinV. Results: As confirmed by Western blot analyses, expression of the mutant proteins was almost completely suppressed in the presence of doxycyclin. Substantial reduction in proliferation was achieved by expression of both wildtype E1A and E1AdelCR2. Expression of E1AdelCR2 was sufficient by itself to induce apoptosis in 8,7% of ovarian carcinoma cells as shown by an increase of the fraction of Annexin binding OVMZ-8 cells. A strong synergistic effect with an increase of the fraction of apoptotoc cells by 16.7% was found when the cells were treated with paclitaxel. Conclusion: Deletion of the CR2 sequence should increase the safety of therapeutic applications of E1A without affecting tumor suppression. A doxycyclin-regulated expression system was established allowing the elucidation of the mechanisms underlying the therapeutic effects of E1A in ovarian cancer cells in the future by means of expression profiling and quantification of activated components of signal transduction pathways.

No significant financial relationships to disclose.

Haem oxygenase-1: a novel player in cutaneous wound repair and psoriasis?

Haem oxygenase (HO) is the rate-limiting enzyme in the degradation of haem. In addition to its obvious role in iron metabolism, a series of findings indicate an important role for HO in cellular protection against oxidative stress. This effect might be of particular importance during wound healing and also in inflammatory disease. Therefore we determined the expression of the two HO isoenzymes, HO-1 and HO-2, during the healing process of full-thickness excisional wounds in mice. We show a remarkable induction of HO-1 mRNA and protein expression within three days after skin injury. After completion of wound healing, HO-1 expression declined to basal levels. By contrast, expression of HO-2 was not significantly modulated by skin injury. In situ hybridization and immunohistochemistry revealed high HO-1 expression in inflammatory cells of the granulation tissue and in keratinocytes of the hyperproliferative epithelium. A strong overexpression of HO-1 was also observed in the skin of patients suffering from the inflammatory skin disease psoriasis. In addition, HO-2 mRNA levels were increased in the skin of psoriatic patients. Similar to wounded skin, inflammatory cells and keratinocytes of the hyperthickened epidermis were the major producers of HO-1 in psoriatic skin. In vitro studies with cultured keratinocytes revealed a potential role for reactive oxygen species (ROS), but not for growth factors and pro-inflammatory cytokines, as inducers of HO-1 expression in inflamed skin. Our findings suggest a novel role for HO in wound healing and inflammatory skin disease, where it might be involved in haem degradation and in the protection of cells from the toxic effects of ROS.

Alkoxypsoralens, novel nonpeptide blockers of Shaker-type K+ channels: synthesis and photoreactivity

A series of psoralens and structurally related 5,7-disubstituted coumarins was synthesized and investigated for their K+ channel blocking activity as well as for their phototoxicity to Artemia salina and their ability to generate singlet oxygen and to photomodify DNA. After screening the compounds on Ranvier nodes of the toad Xenopus laevis, the affinities of the most promising compounds, which proved to be psoralens bearing alkoxy substituents in the 5-position or alkoxymethyl substituents in the neighboring 4- or 4'-position, to a number of homomeric K+ channels were characterized. All compounds exhibited the highest affinity to Kv1.2. 5,8-Diethoxypsoralen (10d) was found to be an equally potent inhibitor of Kv1.2 and Kv1.3, while lacking the phototoxicity normally inherent in psoralens. The reported compounds represent a novel series of nonpeptide blockers of Shaker-type K+ channels that could be further developed into selective inhibitors of Kv1.2 or Kv1. 3.

Biochemical and phylogenetic characterization of the dUTPase from the archaeal virus SIRV

The derived amino acid sequence from a 474-base pair open reading frame in the genome of the Sulfolobus islandicus rod-shaped virus SIRV shows striking similarity to bacterial dCTP deaminases and to dUTPases from eukaryotes, bacteria, Poxviridae, and Retroviridae. The putative gene was expressed in Escherichia coli, and dUTPase activity of the recombinant enzyme was demonstrated by hydrolysis of dUTP to dUMP. Deamination of dCTP by the enzyme was not detected. Phylogenetic analysis based on amino acid sequences of the characterized enzyme and its homologues showed that the dUTPase-encoding dut genes and the dCTP deaminase-encoding dcd genes constitute a paralogous gene family. This report is the first identification and functional characterization of an archaeal dUTPase and the first phylogeny derived for the dcd-dut gene family.

Characterization of apamin-sensitive Ca(2+)-activated potassium channels in human leukaemic T lymphocytes

1. The whole-cell recording mode of the patch-clamp technique was used to study the effect of extracellularly applied ions, toxins and drugs on voltage-independent, apamin-sensitive Ca(2+)-activated K+ channels, K(Ca), expressed in the Jurkat human leukaemic T cell line. 2. Extracellular Ba2+ and Sr+ produced a voltage-dependent block. The equilibrium dissociation constant of the Ba2+/K(Ca) channel complex increased e-fold for a 20 mV change of potential. Ba2+ block of Jurkat K(Ca) channels is therefore as steep as expected from the movement of a single divalent cation about half-way into the electric field of the membrane from the outside. 3. We determined the ion selectivity as well as the conductance of these channels. Calculated permeability ratios, PX/PK, for these K(Ca) channels were 1.0, 0.96, 0.26 and 0.53 for K+, Rb+, Cs+ and NH4+, respectively. Conductance ratios, gX/gK, for the same ions were 1.0, 1.0, 0.67 and 0.11, respectively. Most strikingly this channel can also carry significant current with Cs+ as current carrier. 4. Scyllatoxin (ScTX), a thirty-one amino acid peptide toxin, reduced current through these K(Ca) channels with a half-blocking concentration of approximately 0.3 nM independent of the pH. Other drugs that were able to reduce current through these channels include the classical calcium antagonists diltiazem and verapamil. In contrast, nifedipine, clotrimazole and kaliotoxin (100 nM) were unable to block current through these channels in Jurkat T cells.

[Kasabach-Merritt syndrome. Intraoperative heparin therapy with follow-up combination therapy of heparin and ticlopidine for the control of intravascular coagulation]

A 39-year-old woman with Kasabach-Merritt syndrome (cavernous vascular malformations with disseminated intravascular coagulation) sustained a displaced fracture of the femoral shaft. Despite pronounced hypofibrinogenemia (< 0.1 g/l) there was no significant bleeding. The concentration of D dimer was raised to > 32 < 64 mg/l and that of prothrombin fragments F1 and F2 to > 10 nmol/l. The platelet count was 102,000/microliters and other coagulation parameters were normal or only slightly abnormal. The consumption coagulopathy was successfully controlled by continuous intravenous infusion of heparin (17,000 I.U./d) without need for clotting factor replacement, and was subsequently stabilized by combined treatment with low molecular weight heparin (5,000 I.U./d s.c.) and ticlopidine (250 mg twice daily by mouth). Oral therapy with acetylsalicylic acid alone or in combination with ticlopidine proved insufficient, being rapidly followed by a renewed fall in fibrinogen level and platelet count. The findings suggest that fibrin formation in the abnormal vascular territories was the principal pathogenetic factor in this case.